## Watch the time machine!

Place a thermometer into boiling water, and it will read 100 degrees centigrade. Now plunge the same thermometer into a bucket of ice. The difference in temperature is (at least) 100 degrees, but there is a lag with the thermometer reading. It won’t immediately read 0 degrees, but it will go through the intermediate temperatures (albeit quickly) from 100 degrees, down to 0.

It can easily be argued that the thermometer is in part reading the temperature of itself – it’s own internal temperature, rather than the true ambient temperature.

Keep this in mind as we take an instantaneous journey through time in a time machine…

In an earlier post I demonstrated how the progression of time through space is instantaneous. But how does time progress in a time emachine?

Consider this. A person goes in a time machine and is instantly placed from the present to say 100 years into the future (as far as “instant” is possible…let’s call it experienced time).

Will the watch he’s wearing read t = 0 and instantly transform to t = 100 years? Or like the thermometer, will it pass through all the intermediate times like the thermometer read intermediate temperatures? Will he?

It might seem that a watch, by changing from one state of time to another, intrinsically needs to go through the intermediate times. But this implies a non instant travel. It sounds a little paradoxical that instant time travel means travelling [instantly] through all times in between!

Alternatively, does the watch measure the moment of ambient time, such as a GPS receiver ‘checking in’ to a satellite clock signal? Or does it measure the progression of experienced time?

I mentioned that this particular time machine operates instantaneously. That is to say that the “experienced time” is zero. Ambient time, therefore undergoes an instant change. This raises the question of how is an instant change in time possible?

Let’s pause for a moment on a slight detour and consider a well known thought experiment. On a train.

A train is traveling at a constant speed of 125 mph towards the west. A fly is buzzing in exactly the opposite direction, on a collision path with the train.

The collision inevitably takes place, and I think it’s fair to say that neither the train or the fly are aware of the event.

Now let’s consider the movement of the train and the fly.

The train is moving to the west at constant speed, collides with the fly, and continues its movement to the west (with a very slightly reduced velocity owing to increased combined mass with the fly).

The fly was flying towards the east. It collides with the train, then moves with the train towards the west. This means that the fly’s velocity changes sign, i.e. it goes from an arbitrary positive, through zero, to negative.

At the moment that the fly had zero velocity, it was in contact with the train. It might seem logical to assume that the train must therefore also have a zero velocity…but we know from experience that this is not the case.

We have therefore defined an infinitesimally small moment in time, but how to explain it? (Aside – this is the great thing about time travel – one question leads to another! 🙂 )

I was spinning on a roundabout with my daughters last week trying not to retch. They were fine; they were sitting near the middle, whereas I was on the outer rim. How was it possible that I had a greater linear velocity than they, and yet we were all in contact, much like the fly and the train?

The clue is that we were sitting on the same roundabout, undergoing the same angular velocity. Even the infinitesimally small point in space in the dead centre…was still rotating at the same rate as the rest of us.

And there it is. Angular velocity. I suppose that it’s not for nothing that people talk about the wheel of time! 😉

So back to our question of how is local ambient time experienced in an instantaneous time machine. Could it be that the local time is compressed or contracted to a point of ‘zero time’, (not to be confused with t = 0, an arbitrary reference time point) and regrows back to a new time? This zero time point would be analagous to the ‘fly point’ of zero velocity, or the zero space point on the roundabout.

Progression along the radius of the roundabout maintaining constant angular velocity showed that these zero points are possible. How that can be translated to time, or get it to regrow again…well there lies the magic of a time machine!

## Time in an Instant

There is nothing instant about “instant”.

Not in coffee, not in two shakes of a lambs tail (or a coffee spoon) and not in love at first sight.

I’ve harped on before about the importance of the speed of light, and how nothing can go faster than it.

In the latter article I gave the example of the Earth rotating around a non existent sun after for some reason the sun ceased to be; the transmission of information that the sun ceased to be (one parameter being the existence of gravity) would take some 8 minutes to reach the Earth. The Earth would therefore remain in orbit around a non existent sun for those transitional 8 minutes.

Archimedes had his brainwave whilst he was taking a bath. I had mine during a shower, watching the waste water spiral down through the plug hole. In true Archimedian style I thought to myself “Screw it.”

Why? Surely there must be something out there that can exceed the speed of light.

And I might have found it.

Let’s return to our orbiting Earth (or at least, remain firmly affixed to it’s surface, thanks to our gravitational friend).

As far as we are concerned, sitting (or showering) on the Earth, everything is hunky dory until the Sun disappears, the light goes out and we are flung into space obeying Newton’s second law of motion (i.e. that we travel in a straight line at constant speed unless an external force [in this case, the Sun’s gravity] is applied.

We know that the sun must have vanished 8 minutes ago, so let’s call that moment t = 0 and the present t = 8.

So from the perspective of the Earth at t = 8 we know that the sun vanished at t = 0.

And on the sun, the sun vanished at t = 0. At the same time, i.e. at t = 0. The event of our hindsight knowledge and the event itself was simultaneous.

Is hindsight instantaneous?

I think the example shows that the progression of time across space is instantaneous, although I do concede that it’s a bit strange to give time a speed when it is itself a term in the equation! (speed = distance divided by time!

I’ll conclude with a quote from Bill Nye (more time and time travel quotes here):

â€œWhen we see the shadow on our images, are we seeing the time 11 minutes ago on Mars? Or are we seeing the time on Mars as observed from Earth now? Itâ€™s like time travel problems in science fiction. When is now; when was then?â€ â€“ Bill Nye.

Paul